The goal of this project is to clinically use magnetic resonance imaging (MRI) to control and monitor this thermal therapeutic procedures proposed in the clinical projects in this program. It has been shown that MRI can be effective for visualizing temperature changes in tissues associated with the absorption of non-ionizing therapeutic applications, but are generally in the changes 0.5-1.0 degrees Centigrade, 0.5-1.0 cc voxel size, and 6-20 seconds measurement acquisition time. These resolution ranges imply that MRI can play an important role as a non- invasive tool in the development and application of thermal therapies. In particular, we pose the hypothesis that: Magnetic resonance imaging can be used to control the energy rate of distribution (ARD) and monitor temperatures during thermal therapeutic procedures involving large tumor volumes. We will test these hypothesis using the following specific aims: 1. Develop robust MR thermal imaging techniques for in vivo applications. 2. Develop MRI based feedback control algorithms for the energy absorption rate distribution. Demonstrate ARD control and temperature monitoring in patients having tumors of the lower extremity, based on temperature data acquired with MR chemical shift and/or effective diffusion constant images. Demonstrate ARD control and temperatures monitoring in patients having tumors in the lower abdomen and pelvis with temperature resolution of 0.75-1.25 degrees Centigrade in 1 cc voxels.